Guyed towers and poles provide elevated support for numerous RF related transmitting and receiving equipment including commercial broadcasting, telecommunications, including cellular and PCS equipment, and meteorological monitoring equipment. These structures also support telephone and electrical transmission cables. The lateral support offered to the structure by the guy wire is terminated at a steel guy wire anchor rod which in turn is terminated at a buried “dead man” style anchor block. The anchor block provides the structural resistance to counter the uplift and lateral forces transferred from the tower through the guy wires which result from the wind forces on the structure.
The sole link between the guy wires and the resisting anchor block is the guy wire anchor rod. This rod is typically a steel member with a guy wire equalizer plate welded to the upper end and a concrete embedment tail welded to the lower end. Approximately 20% of the rod is embedded in the concrete anchor and 10% extends above ground level. The remaining 70% is buried and in direct contact with the soil.
The buried portion of the anchor rod is subjected to the detrimental effects of bending stress, electrolytic and galvanic corrosion, any of which can result in the guy wire anchor failure and subsequent total tower failure. Unfortunately, tower collapse due to galvanic corrosion and subsequent anchor rod failure is a well documented and highly publicized phenomenon, the frequency of which continues to increase. In a recent advertising campaign, the National Association of Tower Erectors (NATE) recommended anchor rod inspections be completed prior to any tower work, out of concern for climber safety.
Because the critical anchor rod structural member is buried, most methods of inspection are not helpful. The current method of inspection requires excavation of at least a significant portion of the anchor rod to visually inspect the outer surface. Although this method will detect surface corrosion, it will not reveal stress fractures or other internal anomalies in the steel member. Excavation of the rod is labor intensive and requires supplemental anchor support. The excavation process also subjects the anchor rod to physical harm and the potential of injury to the protective galvanized coating. Excavation also places the worker in a potentially dangerous work position.
U.S. Pat. No. 6,311,565 issued to Hinz et al. proposed solving these shortcomings by providing methods useful for in-field (or remote) analysis of rod integrity without excavation of soil by transmitting ultrasonic energy from the above ground end of a rod to its buried end and receiving the energy returned therefrom. One drawback to this method is that the head end of the rod is welded to the equalizer plate rendering it inaccessible from the exterior of the plate. As such, before an ultrasound transducer can be placed upon the above ground end of the rod, weld material connecting the rod to the associated equalizer plate must be removed to create a small flat surface at or adjacent the head end of the rod and perpendicular to the longitudinal axis of the rod.